there are a couple of options available to you to bring the dogwood down in size and still look acceptable. rejuvenation pruning is one method. this would mean once the plant is dormant this fall or early next spring before growth resumes that you prune it down to the ground as close as you can. The root system will generate new buds and you will have a brand new, but smaller dogwood by mid summer. future pruning would then be to do as you have suggested, pruing out the oldest (tallest) branches at the soil line to help maintain the size. The second method is call renewal pruning where you do remove a portion of the oldest branches at the soil line and use heading back cuts on the remainder to reshape the remaining limbs and control size. This is done over 2-3 years until all the old growth is again removed. it is perfectly ok to use heading back cuts during the growing season to control plant growth with either method. You could use the heading back cuts right now to find your porch and front door again and begin either method next year.